I'm having a service by an indie and can choose my own oil. Present oil is GM Dexos 2 5w30 FS BMW LL - O4 spec. As it is a twin turbo just wondering if this is the best grade as see there is 5w40 but would this be too thick for the turbo. I note BMW have reduced oil change intervals to 10Kmiles but not sure if that is applicable to the N54. Not a real problem mileage wise as I do less than this in 2 years.